In Craig, U.S. Pat. No. 4,286,370 (issued Sept. 1, 1981), there is disclosed a hinge suspension system for inertially sensitive devices made from a single cylindrical member having portions thereof removed by an electro-discharge cutting technique to separate the cylindrical member generally along parallel planes perpendicular to the cylindrical axis. The three cylindrical portions are joined together through two sets of a pair of diametrically opposite, monolithic flexure hinges. Each set of flexure hinges forms a flexure axis about which connecting cylindrical portions may rotate and which is perpendicular to the common axis of the three cylindrical portions. The flexure axes formed by the two sets of flexure hinges are mutually perpendicular. Each flexure hinge is formed by separate crossed leaves which extend between the cylindrical portion at an acute angle to the common axis of the three cylindrical portions. The leaves are mounted axially such that both leaves are in compression when the common axis is vertically positioned. This mounting can result in an isoelastic drift or frequency sensitivity of the flexure hinge which in turn may result in G-sensitivity drift of the resulting device. G-sensitivity must be corrected by electrical circuit or by software in a processor.
Haberland, in U.S. Pat. No. 4,261,211 (issued Apr. 14, 1981), discloses a monolithic hinge of the same type as in the Craig patent except that the leaves of the flexure hinge are joined together at central crossing portions thereof so that the flexure takes place about an axis passing through the crossed leaves. The hinge also has an axial mounting whereby the flexure has same G-sensitivity drift problems as the Craig device.
Barnett, in U.S. Pat. No. 3,543,301 (issued Nov. 24, 1970), discloses a flexural spring pivot of a disc type in which the flexures are formed between three concentric annular rings. The flexures are in the form of leaves which are mounted between adjacent rings.